Vehicle speed and cruise control system

ABSTRACT

A vehicle speed control system is disclosed in which a first train of pulses, at a frequency directly related to actual vehicle speed, is generated. Also generated is a second train of pulses at a frequency which is directly related to maximum vehicle speed. The frequency of the second pulse train is controlled either manually or by the code of any one of a plurality of coded signals received by the system&#39;&#39;s receiver from a low power transmitter. When the frequency of the first train exceeds that of the second train, a restraining force is generated which is applied to the vehicle&#39;&#39;s throttle mechanism in opposition to the force or pressure applied by the operator&#39;&#39;s foot.

United States Patent [191 Permut et al.

[4 1 Oct. 9, 1973 VEHICLE SPEED AND CRUISE CONTROL SYSTEM [22] Filed:May 13, 1971 [21] Appl. No.: 143,079

[52] US. Cl. 180/98, 246/63 A, 246/187 B,

' 317/5 [51] Int. Cl 860k 31/00 [58] Field of Search 180/98, 105, 105 E,

3,482,090 12/1969 Wilcox 246/187 B X 3,599,154 8/1971 Carol 317/5FOREIGN PATENTS OR APPLICATIONS 964,974 7/1964 Great Britain 246/187 BPrimary Examiner-Kenneth H. Betts Attorney-John R. Manning, Monte F.Mott and Paul F. McCaul [57] ABSTRACT A vehicle speed control system isdisclosed in which a first train of pulses, at a frequency directlyrelated to actual vehicle speed, is generated. Also generated is asecond train of pulses at a frequency which is directly related tomaximum vehicle speed. The frequency of the second pulse train iscontrolled either manually or by the code of any one of aplurality ofcoded signals received by the systems receiver from a low power [56]References cited transmtiltlter. gvtlgen the frfqtue ncy of 1126 firsttit ain es- UNITED STATES PATENTS cee s at o e secon ram, a res ra ningorce 1S generated WhlCh 15 applied to the vehicle s throttle 93mechanism in opposition to the force or pressure apml 1 3,207,255 9/1965l-lahlganss... 180/105 R phed by the operator 5 3,476,204 11/1969 Westby180/98 17 Claims, 7 Drawing Figures JLFLFC I VEHICLE f I SPEED FREQ- v I'ND'CATOR COMPARATOR I I fms 28 I Y 22 I Y 20 26 l l c005 SIGNAL PULZSETRANSMITTER I RCVR TO FREQ. conv. SHAPER I I THROTTLE I MANUAL V INPUTCONTROL MECIJATIYICAL NIT U I I U I MECHANISM PAIIIIIEIII 9AA 3,763 ,954

SHEET 10F 3 IO T2 IT 3o vEI-IIc LE mi fv SPEED FREQ- v INDIC COMPARATORfms 28 Y 22 I Y 20 23 26 CODE SIGNAL PULSE TRANSMITTER RcvR To 1 FREQ.coNv. SHAPER THROTTLE MANUAL V INPUT CONTROL SmF MEcI-IANIsM 38 34 32 38 46 I I F|G 2 fi'g d INPUT UNIT sELEcToR 23 2O 42 5O 44 45 I T RcvRDECODER DAC vco COMP- ENABLE ALBERT A. PERMUT VEHICLE COMPASS DIRECTIONARATOR RONALD M. PERMUT CODER ALAN R.PERMUT INVENTORS ATTORNEYS PATENTEU3,763,954

SMU L'UF 3 CLOCK A 5| 55 COUNTER DAC V V SUBTRACTOR MOTOR T0 fms COUNTERDAG Vms 34 v GATE ME :HAN|cA To UNIT 34 FIG. 4

ONE DETECTOR SHOT ACCEL. SENSOR 63 FIG. 5 5 5L5 58 65 COUNTER DAC VvSUBTRACTQR REV. To

MOTOR 34 fms COUNTER DAG Vms GATE BRAKE 52 56 68 66 PEDAL j 67 GATESsuBTRAcToR ALBERT A PERMUT RONALD NLPERMUT 7o ALAN R. PERMUT MANUALINVENTORS CONTROL UNIT BY wfiw %f;/'

I ATTORNEYS PATENTEU 9W6 mm to mm wmm OP om wumnom op mml, mm i lllil W71A,? N. n* mm uomnom $539; om mm 85 |l|| mm! emm wn ow 9w E IIIIII L AL ALBERT A. PERMUT RONALD M PERMUT ALAN R. PERMUT INVENTORS /z WW Z WATTORNEYS VEHICLE SPEED AND CRUISE CONTROL SYSTEM ORIGIN OF INVENTIONThe invention described herein may be manufactured and used by or forthe United States Government without payment of any royalty thereon ortherefor.

BACKGROUND OF THE INVENTION l. Field of the Invention The presentinvention generally relates to speed control devices and, moreparticularly, to a system for controlling the speed ,of highway vehiclesand the like.

2. Description of the Prior Art In the past various systems and deviceshave been proposed for the control of vehicular traffic. The basicprinciple underlying the operation of such systems or devices is thesupply of a speed-defining signal which is transmitted to movingvehicles to control the speed of each vehicle. In practice, thetransmitted signal which is received by the vehicle is the one whichcontrols a vehicle-bearing system, which in turn provides a speedcontrolling output. Such systems suffer from several significantdisadvantages. First, the transmitted signal, typically an RF modulatedsignal in analog form, is subject to noise interference, temperaturedrift and signal strength variations, due to continuous changes in thedistances of the vehicles from the signal transmitters. These factorsgreatly effect the accuracy with which the speed is controlled. Also,since the same speed-defining signal is transmitted to all vehicles, dueto the inherent differences between vehicles, individual adjustment ortailoring of the control circuits in the various vehicles is required.These disadvantages greatly limit the practical use of prior-suggestedsystems. A need therefore exists for a new vehicle speed control systemwhich does not suffer from the above disadvantages and limitations.

OBJECTS AND SUMMARY OF THE INVENTION It is a primary object of thepresent invention to provide a new improved vehicle speed controlsystem.

Another object of the present invention is to provide a new vehiclespeed control system which is substantially uneffected by amplitudevariation and noise conditions of a signal transmitted to each vehicle.

A further object of the invention is the provision of a vehicle controlsystem for each type of vehicle which does not require individualadjustments of control circuitry in each vehicle.

Still a further object of the invention is the provision of a newvehicle speed control system in which the transmitted signal is otherthan the basic control speed signal.

Yet a further object of the present invention is to provide a vehiclecontrol system which is adapted for use on all types of trafficconditions, such as city streets, freeways and interurban highways andwhich is capable of controlling the speeds of vehicles in each of twodirections at the same time.

These and other objects of the invention are achieved by providing asystem in each vehicle which essentially operates in the digital domain.The system includes a unit which generates a first train of pulses at afrequency which is directly related to the actual vehicle speed. Inaddition the system includes a variable frequency oscillator or pulsegenerator which provides a second train of pulses at a frequency whichdepends on a control signal supplied to the generator. The frequenciesof the two trains of pulses are compared and whenever the frequency ofthe first pulse train is greater than the frequency of the second pulsetrain an output signal is produced. This signal, whose magnitude isrelated to the frequency difference, is used to produce a restrictingforce on the vehicle throttle control mechanism which is in oppositionto the foot force or pressure, applied by the vehicle operator. Thus,the operator is immediately made aware of the vehicle's excessive speed.

The system in each vehicle further includes a receiver which receives acoded signal whose decoded characteristics are applied to the pulsegenerator to control the frequency of the pulses supplied thereby. Inaccordance with the present invention, the coded signal is received froma low power transmitter which can be controlled in any conventionalmanner to provide the desired coded signal for controlling the speed ofvehicles in the traffic zone which the transmitter is to control.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will best be understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of oneembodiment of the invention;

FIGS. 24 are block diagrams of various sub-systems shown in FIG. 1;

FIG. 5 is a partial block diagram of another embodiment of theinvention; and

FIGS. 6 and 7 are diagrams useful in explaining a specific embodiment ofsome of the circuitry shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, referencenumeral 10 designates the system of the present invention which is diagrammed in block form. It includes a vehicle speed indicator 12 whoseoutput is a train of pulses, such as squarewave pulses 14, produced at afrequency which is directly related to actual vehicle speed. Thisfrequency will be referred to hereafter as the vehicle speed frequencyand will be designated f,,.

Also included in the system 10 is a receiver 20 which is assumed toreceive a carrier-modulated coded signal from a remotely locatedtransmitter 22. After carrier demodulation the extracted coded signal issupplied to a code to frequency converter 23. Briefly, therein the codedsignal is decoded and the decoded signal is used to activate a latchablevariable frequency oscillator. The output frequency of the oscillator isdirectly related to the characteristics or code of the decoded signal.The converter 23 includes a latchable feature which enables theoscillator to supply a constant output frequency in response to the lastreceived coded signal until a new coded signal is received. Thus, theinput to converter 23 is a succession of discrete coded signals ratherthan a continuously supplied signal.

In practice each time the vehicle enters the transmission range of adifferent transmitter, a new coded signal, which may differ from apreviously received coded signal, is received. However, until the newcoded signal is received the output frequency of the oscillatorcorresponds to the last received coded signal.

The output of converter 23 may be shaped by a pulse shaper 26 whoseoutput pulses have the same shape, such as squarewaves 28, as the pulsesfrom unit 12 and at a frequency identical with the output frequency ofthe oscillator. The code of the coded signal which is transmitted andreceived by receiver 20 represents the desired maximum vehicle speed.Since the output frequency of the shaper 26 is' directly related to thecode of the coded signal, it will be referred to as the maximum speedfrequency and will be designated by f,,,,.

In accordance with the teachings of the present invention, the twofrequencies f,, and f,,,, are compared in a frequency comparator 30whose output is an analog signal, such as a voltage V, whose amplitudeis related to the difference between f, andf V is zero whenever f, g f,and is proportional to the difference f,,f,,,, when f,, f,,,,. Thus,

V when f, f

This voltage is applied to a mechanical unit 32, such as a motor, whosefunction is to apply a force proportional to V to the vehicles throttleactuator mechanism, designated by numeral 34 and hereafter simplyreferred to as the throttle mechanism. The force which is applied to thethrottle mechanism is a restraining force which is in opposition to theoperators foot pressure.

In operation as long as the vehicle speed is not greater than thedesired maximum speed, as defined by the code of the last received codedsignal f,. s f,,,,. Thus V is zero and no restraining force is appliedto the throttle mechanism in opposition to the operators foot pressure.However, as soon as the vehicle speed exceeds the maximum speed, arestraining force in opposition to the operator's foot pressure isapplied. Consequently, the operator becomes immediately aware of theexcessive vehicle speed. The restraining force, whose magnitude isdirectly related to the difference between the vehicle speed and maximumspeed, reduces to zero as soon as the vehicle speed is not greater tothe maximum speed, i.e., when f, s f,,,,.

As is appreciated in accordance with the teachings of the presentinvention, each different code of the coded signal defines a differentmaximum speed. This speed may vary from zero mph to a maximum of speedlimit, e.g., 70 mph. If desired, the maximum speed may be incremented inincrements, e.g., mph. Thus, to vary the maximum speed from 0 to 70 mphin 5 mph increments, the receiver 20 and unit 23 have to be able toreceive up to different coded signals, decode them and activate theoscillator to provide any one of 15 frequencies.

Since different vehicles have different wheel sizes and gear ratios, itis important that in each particular vehicle its f, for a particularspeed corresponds to f, provided by the oscillator when a coded signalcorresponding to the particular speed is received. Upon installing thesystem 10, this may be accomplished by either adjusting the frequenciesprovided by f, as a function of vehicle actual speed, or by adjustingthe frequencies to be provided by the oscillator in each of its 15different latchable conditions. However once such initial adjustmentsare made, no further adjustments are required.

In practice for each make of vehicle with a specific axle ratio andwheel size, the system may include a differently set oscilator so thatwhen a coded signal representing a desired speed is received, theoscillator in each vehicle produces an output frequency f, whichcorresponds to the frequency f,. which the vehicle would produce whenits speed equals the desired speed. This would eliminate the need toadjust each individual system after it is installed in the vehicle. Ifdesired, unit 23 may be made to respond to an external manual settingfrom a manual input unit 38. Such manual setting would define themaximum desired speed. As will be pointed out hereafter, when a manualexternal setting is employed, the system would control the maximum speedto be either that defined by the coded signal or the manually set speedwhichever is smaller.

As is appreciated, various presently known devices and techniques may beused and adapted to provide f,, as a function of vehicle actual speed.Likewise f may be generated with known devices and techniques to be anyone of a plurality of discrete frequencies, e.g., 15, in response to anyone of a plurality of received coded signals. As will be pointed outhereafter, digital circuit ry is pi'imarily employed to compare f,. andf,,,, and provide a voltage output whose amplitude depends on therelationship between the two frequencies. Digital design techniquesgreatly increase circuit reliability. Once the voltage V is produced,any one of many implementations may be employed to provide a restrainingforce which is proportional to V to the vehicles throttle mechanism inopposition to the operator's foot pressure.

From the foregoing description it should be apparent that the presentinvention differs from the prior art in several very significantaspects. In the prior art, the transmitted signal is the control speedsignal and is the same for all vehicles. This requires repeatedindividual tailoring of the vehicle control circuits, resulting in lessreliability, higher cost and greater inaccuracy. Also the transmittedsignal is generally a continuous analog signal, which due to its analogcharacteristics is subject to normal amplitude changes due totemperature drift, signal strength changes and in addition subject tonoise interference. Furthermore, unlessvery powerful transmitters areused in close proximity signal level changes occur over significant zonedistances, thereby affecting the speed control of vehicles, travellingin opposite directions.

Unlike such disadvantages in the present invention, coded signals aretransmitted. Due to their coding their reception is substantially immuneto amplitude variations and/or the effect of noise. Also, since theyneed not be transmitted continuously due to the latching properties ofunit 23, low power transmitters can be used. These need only be locatedat strategic locations such as highway on-ramps and off-ramps or lightlydispersed within specific speed zones to transmit to the vehicle a codedsignal only where a change of speed may be required. However, betweentransmitters, no signal need be received since the maximum speed isdefined by the last received coded signal.

Also, since with the present invention low power transmitters arerequired, transmitters controlling the speed of vehicles travelling inopposite directions may be located on opposite sides of a road. Ifdesired, each unit 23 may incorporate a magnetic compass whose outputwould define vehicle heading. The coded signals could include a headingindication so that each vehicle would respond only to the coded signalsfor its direction. For example, assuming a highway in a north-southdirection, vehicles travelling northward would respond only to codedsignals with a northward heading indication, while those travellingsouthward would respond to the coded signals with a southward headingindication. Such an arrangement would insure failproof separate speedcontrol for vehicles travelling in opposite directions.

In accordance with the present invention digital rather than analogtechniques and devices are employed wherever possible to minimize thesystem's sensitivity to voltage level and waveform changes. Herein, thespeed comparison is based on comparing frequencies which in essencerepresents pulse counting, which can be implemented with present dayintegrated circuitry to save space and cost.

Attention is now directed to FIG. 2 which is primarily a block diagramof but one possible implementation of the unit 23, needed to provide f,as a function of received coded signals. As previously stated, thereceiver output which is the received coded signal is decoded by adecoder 42 and the signal code which is in digital form activates adigital-to-analog (D/A) converter 44, whose output is assumed to be avoltage. The amplitude of the output voltage of the converter isdirectly related to the code of the received signal. It is supplied toan oscillator 45, which is assumed to be a voltage controlled oscillatoror VCO, through an input selector 46.

In operation when unit 38 is not set, selector 46 supplies oscillator 45with the output of converter 44. However, when unit 38 is set, selector46 supplies oscillator 45 with either the output of unit 38 or converter44, whichever is smaller. This enables the system to define the maximumspeed as that set manually as long as it does not exceed the speeddefined by the coded signal. For'example, assuming that the receivedspeed is 50 mph, the operator may set the speed to be less than 50 mph.If however, he sets the speed for more than 50 mph, the received speedas defined by the output of converter 44 will be used for speed control.By selecting the converter 44 to include digital stages, such asflip-flops, which are clocked by the output of receiver whenever a newcoded signal is received, the converters output will change only when anew coded signal is received, but will remain constant between thereception of two successive coded signals. Thus, the latching feature ofunit 23 is achieved.

When unit 23 includes a compass 47 to indicate vehicle direction, itsoutput activates a coder 48 which provides a code indicating vehicledirection. In such an arrangement the received coded signal includes acode of a direction in which traffic is to be controlled by the codedsignal. The decoder 42 supplies the received direction code to acomparator 48' to which the vehicle direction code from coder 48 is alsosupplied. When the two codes are the same, comparator 49 enables a gate50 to enable the received speed code from decoder 42 to be supplied toconverter 44. Thus in this embodiment the converter responds only toreceived coded signals which are designed to control speed in thedirection in which the vehicle travels.

As is appreciated by those familiar with circuit design, various knowndevices may be used to implement the frequency comparator which, aspreviously described, is intended to provide an output voltage which iszero when f, f and one whose amplitude is directly related tof,,f,,,,when f,, f,,,,. Thus, the following description in conjunction with FIG.3 should be regarded as only one possible implementation and is notintended to limit the invention thereto.

As shown in FIG. 3, the comparator 30 comprises a pair of counters 51and 52 to which f,. and f,,,, are supplied, respectively. The twocounters are resettable by the output of a clock 53, which defines apulsecounting period for the two counters. The respective outputs ofcounters 51 and 52 are supplied to D/A converters 55 and 56. Thus theoutput of converter 55 is an analog signal, such as a voltage, relatedto f,., while the voltage output of converter 56 is related to f,,,,.The pulse counting or measuring period, as defined by clock 53, ischosen as a function of the expected maximum frequencies, the bit lengthor maximum count of the two counters, and the desired accuracy so thatduring each counting period, the outputs of converters 55 and 56,designated V, and V, truly represent f, and f,',,,, respectively.

The outputs V and V,,,,, are supplied to a subtractor 58 which subtractsV from V, and provides an output V, which is a function of thisdifference. V,,=0 when V sV However, V,, 0 when V,, V,,,,, i.e., whenthe vehicle speed is greater than the desired maximum speed.

In FIG. 1 V is shown supplied to the mechanical unit 32. The latter mayassume the form of a unidirectional motor, as opposed to a reversible,motor which provides a torque, and therefore the restraining force whichis applied to the mechanism 34. The restraining force is proportional toV,,.

From the foregoing it should be appreciated that in accordance with thepresent invention both the vehicle speed and the desired maximum speed,which is transmitted to the system as a coded signal are converted intorespective frequencies. Digital counters determine these frequencies bycounting them during each counting period. Only when the vehicle speedexceeds the maximum desired speed is a voltage generated, whoseamplitude is related to the speed by which the vehicle speed exceeds themaximum speed. This voltage is converted into a restraining forceapplied to the vehicle s throttle mechanism in opposition to theoperators foot pressure, thereby making the operator immediately awareof the excessive speed.

In practice, the system may further include means to enable the operatorto override the control for a preselected period of time at the end ofwhich the control, i.e., the restraining force is again applied. Suchoverride would be desirable whenever rapid acceleration is needed, suchas in passing another vehicle or in case of a sudden emergency in whichit is desired to move the vehicle from a danger area as fast aspossible.

Such override may be provided by supplying V from comparator 30 tomechanical unit 32 through a gate 61 (see FIG. 4) which is open exceptwhen closed by a disabling signal from a one-shot 62. The system mayfurther include an acceleration sensor 63 which senses sudden changes invehicle acceleration. The output of sensor 63 is supplied to a thresholddetector 64 which supplies a trigger pulse to the one-shot 62 wheneverthe acceleration exceeds a selected value. When the oneshot istriggered, it provides a disabling signal to gate 61, the duration ofthe signal being a function of the one-shot pulse duration. Thus, duringsuch a period chanical unit 32 comprises a reversible motor 65, to

which the output V of subtractor 58 is applied. Also, the motor issupplied with a second input which is the output of a subtractor 66,designated V through a gate 67. Subtractor 66 which is supplied with V,and V,

from converters 55 and 56, subtracts V, from V,,,,. V,= whenever V V,,.However, when V,,,, V,,, the amplitude of V is directly related to thespeed by which V, exceeds V,,.

It should thus be apparent that at any time either V,, or V is zero,except when V,,=V,,,, in which case both V,, and V are zero. WheneverV,,,, is greater than V,,, i.e., the vehicle speed is less than thecruise speed V activates the motor 65 to turn in a first direction toapply a force to the throttle mechanism which activates it in the samedirection as an operators foot pressure to thereby increase the vehiclespeed to the cruise speed. However, when V,, V,,,,, V, is zero and Vcauses the reversible motor to turn in a second direction opposite thefirst direction. As a result, a restraining force is applied to thethrottle mechanism in a direction opposite the direction in which anoperators foot pressure would be applied. Consequently, the vehiclespeed is reduced. Gate 67 is incorporated between subtractor 66 andmotor 65. Gate 67 is closed when the brake pedal is activated. This isdone to prevent the vehicle speed from increasing whenever the oppositeperformance is desired, i.e., vehicle slow down. If desired, once gate67 is closed it can be made to remain closed for a selected time periodbefore full cruise control is again resumed.

As previously stated, the desired cruising speed may be transmitted tothe system and received by the receiver to control f,,,, as previouslydescribed in conjunction with the speed control embodiment. Similarly,the desired cruising speed may be set manually by unit 38 (FIG. 2). Ifdesired V, and V, may be supplied to subtractor 66 through mode controlgates 68 (FIG. 5) which are assumed to be controlled by a manual controlunit 70. For the speed control mode, unit 70 disables or closes gates 68to disable subtractor 66 thereby causing the system to perform the speedcontrol function. On the other hand, when gates 68 are opened by unit70, the system is in the cruise control mode.

It should be stressed that the cruise control system of the presentinvention is unlike any prior art system. In the prior art systems thevehicle speed must first be brought up to desired cruise speed beforethe cruise speed control system takes overautomatic control. In thepresent invention the cruise speed control starts even when the vehicleis not in motion, i.e., when both f, and V, are zero, since the systemis capable of raising the vehicle speed to the desired cruise speed aswell as reduce its speed whenever vehicle speed exceeds the cruisespeed.

Furthermore in the present invention, the maximum cruise speed can bechanged by the coded signals. This would enable traffic officials toincrease or decrease vehicular velocity for optimum traffic flow. Itshould be stressed that in the cruise mode, the cruise speed is eitherthat defined by the coded signals or by the manually set speed, if thelatter is less than that defined by the coded signals. Also, at anyinstant the cruise mode is interruptable by the brake pedal. Inaddition, if desired, the gates 68 may be controlled by specially codedsignals received by receiver 20. This would enable traffic officials toinstitute the cruise control mode remotely. Yet individual drivers mayindividually interrupt this mode by touching the brake pedals of theirvehicles. Such a system would greatly facilitate high density trafficmovement and its control.

Attention is now directed to FIG. 6 which represents another embodimentfor controlling throttle linkage movement and thereby vehicle speed inresponse to V and V,. In this embodiment numeral designates a throttlelinkage which is coupled to a piston 76 in a vacuum chamber 78. Thelinkage 75 is assumed to be connected at its left end to the vehiclethrottle so that when the linkage moves to the left, vehicle speed isincreased, and is decreased when the linkage 75 moves to the right. Atthe right end the linkage extends into a hollow tube-like member 80which is also connected to the vehicles gas or accelerator foot pedal 82through an arm 84. The linkage 75 is locked to member 80 by means of aspring loaded piston 82 of a solenoid 84.

Basically, the piston 76 divides chamber 78 into two vacuum chambers 78aand 78b which are connected through regulators 85 and 86 to a vacuumsource 90. In response to V, which occurs when V,, V,,,,, regulator 86is opened thereby connecting chamber 78b to the vacuum source 90, sothat the linkage is pulled to the right. On the other hand, in thecruise control mode, in response to V which occurs when V,,,, V,,,regulator 85 is opened so that the linkage 75 is pulled to the leftthereby increasing vehicle speed. To provide fast system override, suchas is desired to bypass a vehicle or in case of an emergency, yet limitthe override duration an AND gate 92 is provided. It activates a timedelay unit 94 only when V, is present, i.e., V,, V,,,, and the gas footpedal is pushed down by the operator. After a period defined by thedelay unit 94, the solenoid is activated, pulling piston 82 and therebybreaking the connection between linkage 75 and member 80. Consequently,any further operator force on the foot pedal would not affect theposition of the linkage 75 since such force would merely cause member 80to slide over linkage 75. Means may be provided to deer ergize solenoid84 and thereby reconnect linkage 75 to member 80 after a second timeperiod and/or after the brake pedal is pressed.

Attention is now directed to FIG. 7 which is one example of eitherregulator 85 or 86. It comprises a chamber 95 and a piston 96 whichprovides communication between source and one of the subchambers ofchamber 78 when an appropriate signal (V, or V is applied to a solenoid98. Chamber is provided with a vent port 100 which is opened by a piston102 when a solenoid 104 is energized whenever the brake pedal is pushed.Thus, the operator when pushing on the brake pedal vents bothsubchambers of chamber 78 thereby disengaging the system fromcontrolling vehicle speed.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and variationsmay readily occur to those skilled in the art. For example, the controlof the position oflinkage 75 may be provided by connecting it to twosealed diaphragms which are in turn connected to source 90 throughregulators 85 and 86. One diaphragm would pull the linkage to the leftwhen V,,,, V and the other diaphragm would pull it to the right when V,,V Also, hydraulic means may be provided to couple and decouple linkage75 to and from member 80. Consequently it is intended that the claims beinterpreted to cover such modifications and equivalents.

What is claimed is:

l. A vehicle speed control system comprising:

first means coupled to said vehicle for generating a first sequence ofpulses at a frequency which is directly related to actual vehicle speed;receiving means in said vehicle for receiving a coded signal which istransmitted to said vehicle, the code defining a received maximumvehicle speed;

second means in said vehicle coupled to said receiving means fordecoding said signal to provide a first output which is related to saidreceived maximum vehicle speed;

manually operable means for providing a second output which is relatedto a manually set maximum vehicle speed;

pulse generating means in said vehicle;

selecting means in said vehicle and responsive to said first and secondoutputs and coupled to said pulse generating means for activating saidpulse generating means to provide a second sequence of pulses at afrequency which is directly related to a selected speed which is thesmaller of said received maximum vehicle speed and said manually setmaximum vehicle speed;

third means in said vehicle for comparing the frequencies of said firstand second sequences of pulses and for providing a third output which isa function of the speed with which said vehicle speed exceeds saidselected speed; and

fourth means in said vehicle for utilizing said third output to providea force proportional to said output.

2. The arrangement as recited in claim 1 wherein the vehicle is of thetype operable by an operator and including a throttle mechanism to whichan operatorproduced force is appliable to increase vehicle speed, saidsystem including means for applying the force produced by said fourthmeans to sald throttle mechanism in a direction which is opposite to thedirection in which the operator-produced force is appliable.

3. The arrangement as recited in claim 2 wherein said receiving meansinclude means for receiving any one of a plurality of coded signals,each coded signal of said plurality representing a different receivedmaximum vehicle speed.

4. The arrangement as recited in claim 3 wherein said second meansinclude means for providing said first output which is related to thelast received maximum vehicle speed as represented by the code of thelast received coded signal until the reception by said receiving meansof a subsequent coded signalv 5. The arrangement as recited in claim 3wherein the vehicle is of the type operable by an operator and includinga throttle mechanism to which an operatorproduced force is appliable toincrease vehicle speed,

said system including means for applying the force produced by saidfourth means to said throttle mechanism in a direction which is oppositeto the direction in which the operator-produced force is appliable.

6. The arrangement as recited in claim 4 wherein each coded signalincludes a first direction code defining the direction in which saidreceived maximum vehicle speed is to be maintained, said system furtherincluding means for providing a second direction code defining theactual vehicle direction, and means including code comparing means forcontrolling said second means to supply said first output only when saidfirst and second direction codes are substantially the same.

7. The arrangement as recited in claim 1 wherein said third meansfurther include means for providing a fourth output which is a functionof the speed with which said selected speed exceeds said vehicle speed,and said fourth means comprise means which is responsive to said thirdand fourth outputs for providing a first force in a first directionwhich is a function of said third output and a second force in a seconddirection opposite said first direction which is a function of saidfourth output.

8. The arrangement as recited in claim 7 further including gating meanscoupled to said third and fourth means for selectively inhibit thesupply of said fourth output to said fourth means.

9. The arrangement as recited in claim 8 wherein the vehicle is of thetype operable by an operator and including a throttle mechanism to whichan operatorproduced force is appliable to increase vehicle speed, saidsystem including means for applying the first force in said firstdirection produced by said fourth means to said throttle mechanism in adirection which is opposite the direction in which the operator-producedforce is appliable and for applying the second force in said seconddirection produced by said fourth means to said throttle mechanism inthe same direction in which said operator-produced force is appliable,said vehicle further including a manually operable brake pedal, andmeans for activating said gating means to inhibit the supply of saidfourth output to said fourth means, whenever said brake pedal isoperable.

10. The arrangement as recited in claim 9 wherein said receiving meansinclude means for receiving any one of a plurality of coded signals,each coded signal of said plurality representing a different receivedmaximum vehicle speed.

11. The arrangement as recited in claim 10 wherein said second meansinclude means for providing said first output which is related to thelast received maximum vehicle speed as represented by the code of thelast received coded signal until the reception by said receiving meansof a subsequent coded signal.

12. The arrangement as recited in claim 11 wherein each coded signalincludes a first direction code defining the direction in which saidreceived maximum vehicle speed is to be maintained, said system furtherincluding means for providing a second direction code defining theactual vehicle direction, and means including code comparing means forcontrolling said second means to supply said first output only when saidfirst and second direction codes are substantially the same.

13. A system for controlling the speed of a vehicle adapted to travelover long distances, the system comprising:

first means in said vehicle for generating a first sequence of pulses ata frequency which is directly related to actual vehicle speed; v

receiver means in said vehicle for receiving aperiodically any one of aplurality of coded signals, which are transmitted to said vehicle, eachcoded signal representing a different desired vehicle speed;

second means in said vehicle for responding to the coded signal lastreceived by said receiver means for providing a second sequenceof pulsesat a frequency which is independent of actual vehicle speed and which isa function of the desired vehicle speed represented by said lastreceived coded signal, said second means providing said second sequenceof pulses for the entire duration following said last received codedsignal until a subsequent coded signal is received aperiodically by saidreceiver means;

third means in said vehicle for continuously comparing the frequenciesof said first and second sequences of pulses and for providing a firstoutput which is a function of the speed with which said actual vehiclespeed exceeds said desired vehicle speed; and

fourth means in said vehicle for providing a first force proportional tosaid first output.

14. The arrangement as recited in claim 13 wherein the vehicle is of thetype operable by an operator and including a throttle mechanism to whichan operatorproduced force is appliable to control vehicle speed, saidsystem including means for applying the first force produced by saidfourth means to said throttle mechanism in a direction which is oppositeto the direction in which the operator-produced force is appliable.

15. The arrangement as recited in claim 13 wherein said third meansfurther include means for providing a second output which is a functionof the speed with which said desired speed exceeds said vehicle speed,and said fourth means comprise means which is responsive to said firstand second outputs for providing said first force in a first directionand a second force which is a function of said second output in a seconddirection opposite said first direction.

16. The arrangement as recited in claim 15 wherein the vehicle is of thetype operable by an operator and including a throttle mechanism to whichan operatorproduced force is appliable to control vehicle speed, saidsystem including means for applying the first force in said firstdirection produced by said fourth means to said throttle mechanism in adirection which is opposite the direction in which the operator-producedforce is appliable and for applying the second force in said seconddirection produced by said fourth means to said throttle mechanism inthe same direction in which said operator-produced force is appliable17. A system for controlling the speed of a vehicle operable by anoperator, the system comprising:

first means in said vehicle for generating a first sequence of pulses ata frequency which is directly related to actual vehicle speed which isvariable over a range of n miles per hour, n being not less than 50;receiver means in said vehicle for receiving aperiodically any one of aplurality of coded signals, which are transmitted to said vehicle, eachcoded signal representing a different desired vehicle speed in miles perhour, the smallest difference between ,the desired speeds represented byany two coded signals being not less than 1 miles per hour, where z isan integer, not less than one; second means in said vehicle forresponding to the coded signal last received by said receiver means forproviding a second sequence of pulses at a frequency which isindependent of actual vehicle speed and which is a function of thedesired vehicle speed represented by said last received coded signal,said second means providing said second sequence of pulses for theentire duration following said last received coded signal until asubsequent coded signal is received aperiodically by said receivermeans; third means in said vehicle for continuously comparing thefrequencies of said first and second sequences of pulses and forproviding a first output having an amplitude which is a function of thespeed with which said actual vehicle speed exceeds said desired vehiclespeed; fourth means in said vehicle for providing a first forceproportional to the amplitude of said first output; throttle means insaid vehicle for controlling actual vehicle speed as a function of theforce applied by said operator to said throttle means; and meansforapplying said first force to said throttle means in a direction oppositethe direction in which the'operator force is applied.

1. A vehicle speed control system comprising: first means coupled to said vehicle for generating a first sequence of pulses at a frequency which is directly related to actual vehicle speed; receiving means in said vehicle for receiving a coded signal which is transmitted to said vehicle, the code defining a received maximum vehicle speed; second means in said vehicle coupled to said receiving means for decoding said signal to provide a first output which is related to said received maximum vehicle speed; manually operable means for providing a second output which is related to a manually set maximum vehicle speed; pulse generating means in said vehicle; selecting means in said vehicle and responsive to said first and second outputs and coupled to said pulse generating means for activating said pulse generating means to provide a second sequence of pulses at a frequency which is directly related to a selected speed which is the smaller of said received maximum vehicle speed and said manually set maximum vehicle speed; third means in said vehicle for comparing the frequencies of said first and second sequences of pulses and for providing a third output which is a function of the speed with which said vehicle speed exceeds said selected speed; and fourth means in said vehicle for utilizing said third output to provide a force proportional tO said output.
 2. The arrangement as recited in claim 1 wherein the vehicle is of the type operable by an operator and including a throttle mechanism to which an operator-produced force is appliable to increase vehicle speed, said system including means for applying the force produced by said fourth means to saId throttle mechanism in a direction which is opposite to the direction in which the operator-produced force is appliable.
 3. The arrangement as recited in claim 2 wherein said receiving means include means for receiving any one of a plurality of coded signals, each coded signal of said plurality representing a different received maximum vehicle speed.
 4. The arrangement as recited in claim 3 wherein said second means include means for providing said first output which is related to the last received maximum vehicle speed as represented by the code of the last received coded signal until the reception by said receiving means of a subsequent coded signal.
 5. The arrangement as recited in claim 3 wherein the vehicle is of the type operable by an operator and including a throttle mechanism to which an operator-produced force is appliable to increase vehicle speed, said system including means for applying the force produced by said fourth means to said throttle mechanism in a direction which is opposite to the direction in which the operator-produced force is appliable.
 6. The arrangement as recited in claim 4 wherein each coded signal includes a first direction code defining the direction in which said received maximum vehicle speed is to be maintained, said system further including means for providing a second direction code defining the actual vehicle direction, and means including code comparing means for controlling said second means to supply said first output only when said first and second direction codes are substantially the same.
 7. The arrangement as recited in claim 1 wherein said third means further include means for providing a fourth output which is a function of the speed with which said selected speed exceeds said vehicle speed, and said fourth means comprise means which is responsive to said third and fourth outputs for providing a first force in a first direction which is a function of said third output and a second force in a second direction opposite said first direction which is a function of said fourth output.
 8. The arrangement as recited in claim 7 further including gating means coupled to said third and fourth means for selectively inhibit the supply of said fourth output to said fourth means.
 9. The arrangement as recited in claim 8 wherein the vehicle is of the type operable by an operator and including a throttle mechanism to which an operator-produced force is appliable to increase vehicle speed, said system including means for applying the first force in said first direction produced by said fourth means to said throttle mechanism in a direction which is opposite the direction in which the operator-produced force is appliable and for applying the second force in said second direction produced by said fourth means to said throttle mechanism in the same direction in which said operator-produced force is appliable, said vehicle further including a manually operable brake pedal, and means for activating said gating means to inhibit the supply of said fourth output to said fourth means, whenever said brake pedal is operable.
 10. The arrangement as recited in claim 9 wherein said receiving means include means for receiving any one of a plurality of coded signals, each coded signal of said plurality representing a different received maximum vehicle speed.
 11. The arrangement as recited in claim 10 wherein said second means include means for providing said first output which is related to the last received maximum vehicle speed as represented by the code of the last received coded signal until the reception by said receiving means of a subsequent coded signal.
 12. The arrangement as recited in claim 11 wherEin each coded signal includes a first direction code defining the direction in which said received maximum vehicle speed is to be maintained, said system further including means for providing a second direction code defining the actual vehicle direction, and means including code comparing means for controlling said second means to supply said first output only when said first and second direction codes are substantially the same.
 13. A system for controlling the speed of a vehicle adapted to travel over long distances, the system comprising: first means in said vehicle for generating a first sequence of pulses at a frequency which is directly related to actual vehicle speed; receiver means in said vehicle for receiving aperiodically any one of a plurality of coded signals, which are transmitted to said vehicle, each coded signal representing a different desired vehicle speed; second means in said vehicle for responding to the coded signal last received by said receiver means for providing a second sequence of pulses at a frequency which is independent of actual vehicle speed and which is a function of the desired vehicle speed represented by said last received coded signal, said second means providing said second sequence of pulses for the entire duration following said last received coded signal until a subsequent coded signal is received aperiodically by said receiver means; third means in said vehicle for continuously comparing the frequencies of said first and second sequences of pulses and for providing a first output which is a function of the speed with which said actual vehicle speed exceeds said desired vehicle speed; and fourth means in said vehicle for providing a first force proportional to said first output.
 14. The arrangement as recited in claim 13 wherein the vehicle is of the type operable by an operator and including a throttle mechanism to which an operator-produced force is appliable to control vehicle speed, said system including means for applying the first force produced by said fourth means to said throttle mechanism in a direction which is opposite to the direction in which the operator-produced force is appliable.
 15. The arrangement as recited in claim 13 wherein said third means further include means for providing a second output which is a function of the speed with which said desired speed exceeds said vehicle speed, and said fourth means comprise means which is responsive to said first and second outputs for providing said first force in a first direction and a second force which is a function of said second output in a second direction opposite said first direction.
 16. The arrangement as recited in claim 15 wherein the vehicle is of the type operable by an operator and including a throttle mechanism to which an operator-produced force is appliable to control vehicle speed, said system including means for applying the first force in said first direction produced by said fourth means to said throttle mechanism in a direction which is opposite the direction in which the operator-produced force is appliable and for applying the second force in said second direction produced by said fourth means to said throttle mechanism in the same direction in which said operator-produced force is appliable.
 17. A system for controlling the speed of a vehicle operable by an operator, the system comprising: first means in said vehicle for generating a first sequence of pulses at a frequency which is directly related to actual vehicle speed which is variable over a range of n miles per hour, n being not less than 50; receiver means in said vehicle for receiving aperiodically any one of a plurality of coded signals, which are transmitted to said vehicle, each coded signal representing a different desired vehicle speed in miles per hour, the smallest difference between the desired speeds represented by any two coded signals being not less than z miles per hour, where z is an integer, not less tHan one; second means in said vehicle for responding to the coded signal last received by said receiver means for providing a second sequence of pulses at a frequency which is independent of actual vehicle speed and which is a function of the desired vehicle speed represented by said last received coded signal, said second means providing said second sequence of pulses for the entire duration following said last received coded signal until a subsequent coded signal is received aperiodically by said receiver means; third means in said vehicle for continuously comparing the frequencies of said first and second sequences of pulses and for providing a first output having an amplitude which is a function of the speed with which said actual vehicle speed exceeds said desired vehicle speed; fourth means in said vehicle for providing a first force proportional to the amplitude of said first output; throttle means in said vehicle for controlling actual vehicle speed as a function of the force applied by said operator to said throttle means; and means for applying said first force to said throttle means in a direction opposite the direction in which the operator force is applied. 